This invention relates to the field of assorting apparatus, and particularly to apparatus for separating weakly magnetic particles from the non-magnetic particles of a mixture of the two. Here the word "magnetic" refers to particles which are magnetically susceptible, and is not meant to imply particles which are themselves permanently magnetized. The procedure is very important in modern iron mining operations, where the ore is of relatively low grade and contains much gangue. An example is the operation of taconite mining where the ores are of relatively low grade, contain primarily weakly magnetic iron minerals, and are commonly referred to as "oxidized taconite". Such ores are generally no better than the discarded "tailings" of earlier iron mining operations, and indeed those tailings may become a valuable source of iron by the use of my new separator.
Assorting of solids according to their magnetic properties is not new, and devices are known to perform this function, both with particles in the dry state and with particles in the form of a slurry. Such devices have heretofore had the defect that for successful operation on weakly magnetic materials, it has been necessary to use electromagnetics of tremendous size which required complicated auxiliary cooling facilities and consumed many kilowatt hours of electricity per ton of treated material.